Effect of the Uncertainty About the Fatigue Limit on Highway Bridge Reliability

Abstract: Current fatigue design specifications for welded steel highway bridges subjected to high traffic volumes require the design to be capable of resisting high-cycle, long life conditions without extensive crack growth. Results from laboratory fatigue tests of large-scale welded attachments under random variable loading have indicated that the existence of a fatigue limit below which no fatigue cracks develop is assured only if none of the stress cycles exceed the constant amplitude fatigue limit. However, the value of the constant amplitude fatigue limit is not precisely known and in some cases will differ from the assumed value due to the limited fatigue test database. This paper examines the influence of the variability in the fatigue limit on the fatigue design of bridges.